Generally, a plurality of gears are arranged to be engaged with each other in a driving mechanism. Since gear teeth (teeth addendums) contact each other during engagement, the teeth of the gears often collide during meshing. So far, collision between gear teeth of different gears are prevented by providing a gap between a gear hole and a shaft or by using higher gear teeth. Employing heightened gear teeth in spur gears not only reduces the possibility of collisions between aligned gears, it also provides for more stability between the gears once engaged as there is a smaller chance of slipping when the teeth addendum is greater. Therefore, in many instances, it is desirable to use gears having a heightened tooth design. The benefits of a heightened tooth design in spur gears however can only be realized if the engaging gears are perfectly aligned. Perfect gear alignment is often difficult to achieve consistently, particularly for low cost gear trains designed to be installed in assembly lines. I have consequently found that there is a need for an improved tooth design that reduces the risk of gear teeth collision when gears are slightly misaligned.
There has been some effort in the art to improve the design of gears. For example, U.S. Pat. No. 2,682,760 for a Gear Coupling to Shenk seeks to overcome interference and friction problems during the coupling process of gears, even when the gears are slightly misaligned. Among other things, Shenk seeks to reduce interference by using a tooth design, with the tooth height set in a way such that the teeth are crowned across the face width, thus having the tooth highest half way between the end portions of the gear tooth. I have found that Shenk's design lacks a flat portion on the top of the tooth.
U.S. Pat. No. 3,881,365 titled Gearing to Hardy proposes a tooth design for a gear to cut down on noise generated during operation. Hardy's disclosure addresses the need to correct noise created tooth imperfections and off tolerances. Hardy's design involves tapering the top surface of the tooth along the face width. Hardy's design does not seem to address the problem of misalignment between gear shafts however.
U.S. Pat. No. 2,463,725 for a Method of Cutting Gear Pairs to Stonebraker discloses a novel tooth design for a gear in an effort to provide better contact upon coupling. The height of the tooth or the addendum gradually varies with distance along the face width. U.S. Pat. No. 3,043,158 for a Means for Maintaining a Pair of Mating Gears in Mesh to Herr discloses a novel tooth design for a gear that involves tapering along the face width. U.K. Patent application 2224554A to Hill discloses novel tooth designs for reducing noise and vibrations during operation. There appears to be no disclosure of varying the tooth height along the face width.
Japanese patent 3-28565 A to Morikawa discloses a novel tooth design used to reduce noise and vibration during operation. Morikawa's design involves a chamfer in the gear tooth. German patent 1286361 discloses a novel tooth design for a gear. The tooth height or addendum varies along the length of the face.
Although the prior efforts appear to contain tooth designs for spur gears that both heighten the gear teeth and to correct misalignment between coupling gears, I have found that there exists a need for a gear able to compensate for out-of-parallel alignment between the shafts of successive gears within a train of gears.